The present invention relates generally to a novel air-atomizing oil burner utilizing a low pressure fan, and a three-piece air-atomizing nozzle suitable for use therein. More particularly, it relates to such a novel burner which is configured to provide a uniform mixing of atomized oil and air for consistent ignition and efficient combustion.
Conventional air-atomizing oil burners offer the benefit of partially mixing oil with air prior to discharge from an orifice of a nozzle allowing the burner to operate at low firing rates compared to conventional oil burners which incorporate a pressure atomizing nozzle. In an air-atomizing oil burner, oil passes through the air-atomizing nozzle for combining with a high velocity air stream prior to discharge of atomized oil and air from the nozzle. Typically, a compressor supplies pressurized air at about 10 psi to about 100 psi to provide the required high velocity air supply.
With conventional air-atomizing oil burners, the high cost and unreliability of air compressors has limited the use of air-atomizing oil burners for residential heating. A recent attempt has been made to provide a low firing rate, air-atomizing oil burner suitable for residential heating that uses a low pressure fan powered by an expensive brushless DC motor to supply air at a pressure of about 6 to 12 inches of water (0.21 psi to 0.92 psi). Drawbacks with such air-atomizing oil burners are the complexity and high cost associated with fabricating the air-atomizing nozzle and the inability to regulate the supply of the low pressure air from the fan to provide a stable uniform mixture of atomized oil and air for consistent ignition and efficient combustion.
For example, FIG. 1 shows a diagrammatic illustration of a prior art air-atomizing oil burner 10 having a low pressure fan 12 which provides a primary air supply, a secondary air supply, and a tertiary air supply. Primary air passes through air-atomizing nozzle 20, secondary air passes through a back plate 14 and a retention plate 16, and tertiary air passes between back plate 14 and air cone 18. As best seen in FIG. 2, a drawback with this prior art design is that a plurality of holes 19 in back plate 14 produce high pressure points. The turbulent air which exits holes 19 rushes toward retention plate 16 and discharges out louvers 17. This turbulent secondary air which exits louvers 17 unevenly mixes with the discharge of atomized oil and air from nozzle 20 resulting in inconsistent ignition and uneven combustion.
As shown in FIG. 3, air-atomizing nozzle 20 in burner 10 comprises an outer body 21, an end cap 24, a swirler 26, an inner body 22, a fuel distributer 23 fitted to inner body 22, and a pair of O-rings 28. Thus, this prior art nozzle requires six separate parts which must be precisely machined and subsequently assembled together which obviously makes it relatively expensive.